System and method to pre-ignition in an internal combustion engine

An engine system and method are disclosed for controlling pre-ignition of an alcohol fuel. In one embodiment, the fuel injection timing is adjusted to cause the fuel to avoid combustion chamber surfaces. In another embodiment, the fuel injection timing is adjusted to spray the fuel directly onto the piston surface to cool the piston. Also disclosed is a cylinder cleaning cycle in which engine knock is purposely caused for one to hundreds of engine cycles by adjusting the fuel content away from alcohol toward gasoline. Further measures to cause knock which are disclosed: adjusting spark timing, intake boost, exhaust gas fraction in the cylinder, cam timing, and transmission gear ratio.